The invention relates to metal shredders, and particularly to metal shredders that sense and eject larger objects that jam the shredder.
Machine shops fabricate metal objects by cutting, grinding, bending and welding metal into parts and fastening the parts together with bolts or other fasteners to complete the metal object. During these fabrication processes, metal shavings, chips and the like result from the processing of the metal. It is the practice of most machine shops to collect the shavings, chips and the like for recycling.
There have been several difficulties with recycling the metal shavings, chips and the like. Handling and transporting the shavings, chips and the like from the machine shop to the foundry is inefficient and costly; the shavings, chips and the like are usually laden with cutting oil, requiring costly recycling processes to remove the oil. One solution to these problems is to compact the metal shavings, chips and the like at the machine shop into a form that is easily handled and transported. One such machine for compacting metal shavings, chips and the like is the Puckmaster(trademark) metal compactor available from MCT Manufacturing of Montgomery, Minn. This compactor, which is described in my U.S. Pat. Nos. 5,391,069, 5,542,348 and 5,542,348, compacts metal shavings, chips and the like at high pressures (25,000 to 42,000 psi) to form metal pellets. The pellets have a diameter of about 3xc2xd inches and a thickness between about 1 and 2 inches and, because they resemble hockey pucks, they are known in the trade as xe2x80x9cpucksxe2x80x9d. With the Puckmaster compactor, machine shops can compact scrap shavings, chips and the like, retrieved from sweeping from the machine shop floor. The compacting process extrudes cutting oil from the shavings, chips and the like which is recovered for reuse by the machine shop.
The pellets or xe2x80x9cpucksxe2x80x9d formed from scrap metal shavings, chips and the like by metal compactors like the Puckmaster machine are easily handled and transported to a recycling foundry where the metal is reclaimed from the pellets. Moreover, because the pucks are substantially free of cutting oil, they can be more economically recycled, resulting in higher prices received from recycling foundries for the pucks. These factors result in considerable cost savings to the machine shop, as well as more efficient recycling by the foundry.
The compactor compacts the scrap metal chips and shavings retrieved from the shop floor. In many cases the chips and shavings need to be shredded into a smaller size for compacting. Additionally, small sheet metal scraps discarded by the shop operators are collected with the shavings and chips on the floor to be compacted by the compactor. These sheet metal scraps and the like also need to be shredded before compacting. Accordingly, there is a need for a metal shredder to shred metal scraps into chips and shavings suitable for compacting into pucks by a compactor, such as the Puckmaster compactor. However, larger parts and spare items, such as bolts and brackets, occasionally fall onto the shop floor and are mixed into, and collected with, the metal chips and shavings for shredding and compacting. These larger parts and objects present a problem because they will jam the shredder. Therefore, there is a need for a shredder that automatically ejects the larger objects from the metal chips and shavings before shredding is attempted.
Apparatus is provided for shredding metal shavings, chips and the like and for ejecting larger objects. In one form of the invention, the apparatus includes a housing having first and second opposing walls forming a shredder chamber, an inlet for admitting metal chips and shavings to be shredded into the shredder chamber, an ejection outlet for discharging jamming objects from the shredder chamber, and a shredder outlet for discharging the shredded shavings, chips and the like from the housing. A shredder assembly is mounted in the housing between the shredder chamber and the shredder outlet. The shredder assembly includes a plurality of first knives mounted to a first roller shaft mounted between the first and second walls. A plurality of second knives are mounted to a second roller shaft mounted between the first and second walls, the first and second roller shafts being positioned within the housing so that the first and second knives mesh to shred metal shavings, chips and the like upon rotation of the first and second roller shafts. A motor assembly rotates the first and second roller shafts, and a sensor is operatively associated with at least one of the roller shafts to sense rotation of the one roller shaft. A microprocessor is coupled to the motor assembly to control rotation of the roller shafts. The microprocessor is programmed to, operate the motor assembly to rotate the first and second roller shafts in a shredding direction to draw metal shavings, chips and the like to be shredded into the first and second knives. The microprocessor is further programmed to be responsive to the sensor sensing a change in motion of the one roller shaft due to a jamming object in the first and second knives to first operate the motor assembly to rotate the first and second roller shafts in a reverse direction to dislodge the jamming object from the first and second knives and then to operated the motor assembly to halt rotation of the second roller shaft while continuing rotation of the first roller shaft in the reverse direction to discharge the jamming object to the ejection outlet.
The housing may include an ejection door having a closed position closing the ejection outlet and an open position permitting discharged jamming objects to be ejected through the ejection outlet. A motor control operates the ejection door between its closed and open positions. The microprocessor is further programmed to operate the control to move the ejection door from its closed to its open position when the sensor senses a change in motion of at least one roller shaft due to a jamming object. Preferably, the microprocessor is further programmed to operate the control to move the ejection door from its open to its closed position after the jamming object has been ejected through the ejection outlet.
In one form of the invention, the control includes a door motor for operating the ejection door between its closed and its open position. The door includes a plurality of first and second followers on the ejection door and corresponding first and second guides on each of the first and second walls. The first followers track the first guides and the second followers track the second guides, with the first and second guides being arranged as to guide the followers to pivotly move the ejection door so that as the ejection door pivots from its closed to its open positions, it sweeps shavings, chips and the like from the shredder assembly.
In another form of the invention, the shredder assembly includes spacers on at least one of the roller shafts and between each adjacent knife on the roller shaft to space the knives along the roller shaft. A cleaning assembly is mounted to the housing adjacent at least the first roller shaft. The cleaning assembly has a plurality of cleaning fingers extending into the space between the knives to clean the space of material,
In this form of the invention, the cleaning assembly may optionally include a plurality of guide fingers extending into the space between the first knives to transport dislodged jamming objects to the ejection outlet.
Preferably, the apparatus includes a second cleaning assembly adjacent the second rotation shaft with cleaning fingers arranged to clean material from the space between the second knives. A plurality of second guide fingers extend into the space between the second knives for transporting shavings, chips and the like admitted through the inlet to the first and second knives.